TELKOM
NIKA Indonesia
n
Journal of
Electrical En
gineering
Vol. 13, No. 1, Janua
ry 201
5, pp. 85 ~ 9
0
DOI: 10.115
9
1
/telkomni
ka.
v
13i1.676
0
85
Re
cei
v
ed Se
ptem
ber 29, 2014; Revi
se
d No
vem
ber
19, 2014; Accepted Decem
ber 5, 201
4
A Novel Compact Microstrip Lowpass Filter with Sharp
Transition and Improved Stopband
Pingjuan Zhang*
1
, Minquan Li
2
1
Mathmatics a
nd Informatio
n
Engi
neer
in
g Institute of Anhui
Science a
nd T
e
chn
o
lo
g
y
Un
i
v
ersit
y
,
F
eng
ya
ng 2
3
3
100, Anh
u
i, Ch
ina
2
School of Elec
tronics an
d Informatio
n
Engi
n
eeri
ng,
Anh
u
i
Univers
i
t
y
, H
e
fei 23
00
39, Anh
u
i, Chi
n
a
*Corres
p
o
ndi
n
g
author, e-ma
i
l
: limq@a
hu.e
d
u
.cn
A
b
st
r
a
ct
A nov
el co
mpa
c
t micr
ostrip l
o
w
pass filter (L
PF
) is
pro
pose
d
in
this
pa
per
, w
h
ich cons
ists of t
h
e
compl
e
mentar
y rectang
le sp
l
i
t ring d
e
fecte
d
micr
ostr
ip stru
cture (CRSR-
DMS), ope
n stubs, spur
lin
e a
n
d
the du
mb
be
ll-s
hap
ed d
e
fecte
d
grou
nd struc
t
ure (DGS
). Due to the un
iq
ue resp
ons
e o
f
the presente
d
CRSR-DMS, a
low
passban
d
insertio
n loss
and a shar
p transiti
on of the prop
osed
L
P
F
w
a
s achieved.
Meanw
hi
le,
an
i
m
pr
oved
sto
pba
nd
w
a
s o
b
tain
ed
by
pr
o
p
e
rly
adj
ustin
g
t
he w
o
rki
n
g
fre
que
ncies
of
op
en
stubs, a third-o
r
der LPF
usin
g
spurlin
e an
d d
u
mbb
e
ll-
s
hap
e
d
DGS. T
he measur
ed
resu
lt of the desig
ne
d
LPF
show
s tha
t
attenuati
on ra
te reach
e
s 1
5
9
dB/GH
z
and
a
w
i
de stopb
an
d is o
b
tain
ed fr
om
4.07 GH
z
t
o
mor
e
than 1
5
GH
z
.
Ke
y
w
ords
: lo
w
pass filter, defected microstri
p
structure, defected
gro
u
n
d
structure
Copy
right
©
2015 In
stitu
t
e o
f
Ad
van
ced
En
g
i
n
eerin
g and
Scien
ce. All
rig
h
t
s reser
ve
d
.
1. Introduc
tion
Microstri
p
lo
wpa
s
s filter
(LPF) with
a
small
ci
rcuit si
ze, sha
r
p
tran
sition a
nd wi
de
stopb
and
ha
s be
en hi
ghl
y requi
red i
n
many mi
crowave
com
m
unication
systems to
bl
ock
harm
oni
c an
d spu
r
iou
s
re
spo
n
se ca
used by the fro
n
t-end
circuit
s
[1]. Conve
n
tional micro
s
trip
line ba
sed
L
P
Fs can only
provide
a gradual tr
an
sition and
na
rro
w upp
er
stop
band b
and
wi
dth.
To sha
r
pe
n attenuation
rate
an
d wide
n
up
per
stop
band
ba
nd
wi
dth, m
any pl
anar
resonat
ors,
su
ch a
s
ci
rcular h
a
irpi
n reso
nator [2]
and
comp
ou
nd re
so
nator [3], have been devel
op
ed.
Another m
e
thod to de
sig
n
com
p
a
c
t and high
-pe
r
fo
rman
ce LPF
is to employ
defecte
d gro
und
stru
cture (DG
S
) [4-12] due
to its promi
n
e
n
t stopba
nd a
nd obviou
s
sl
ow-wave effe
ct.
Since e
a
ch DGS unit ca
n gene
rate a
n
attenuation
pole, a wid
e
stopb
and
of LPF is
obtaine
d by utilizing casca
ded DGS unit
s
with differe
nt lengths [4
-5]. Throug
h u
s
e of additio
n
a
l
open
stu
b
s,
stopban
d b
and
width m
a
y be
furthe
r imp
r
o
v
ed [6-7].
Ho
wever, th
e im
plemente
d
L
P
F
often ha
s
a la
rge
physi
cal
size. Usin
g n
o
vel shap
ed
DGS
with m
o
re atten
uatio
n pol
es [8-9]
may
effectively sol
v
e the proble
m
. The
comp
act LPF
m
a
y also
be d
e
si
g
ned b
a
sed o
n
the equival
e
nt
seri
es i
ndu
ct
ance produ
ced by the DGS re
s
onato
r
and the
convention
a
l desi
gn theo
ry of
prototype filter [10-1
3
]. The desig
n pro
c
e
ss of
a five-pol
e LPF u
s
ing du
mbb
e
l
l
-sh
ape
d DG
S is
pre
s
ente
d
in
[11] and th
e
system
atic d
e
sig
n
meth
o
d
for th
e co
mplex DGS
slot ba
se
d L
P
F is
validated in
[12]. For t
he d
e
sig
n
of
com
pact
and
high
-pe
r
form
an
ce
LPF, multilay
e
r te
chni
que
will
be a
good
candid
a
te. For instan
ce, i
n
orde
r to
achieve a
wide
rejectio
n in th
e stop
ban
d, two
ca
scade
d
λ
/2
defected mi
crost
r
ip st
ru
ctu
r
e (DMS) res
onators toget
her
with two vertically lo
cat
ed
DGS resonat
ors
are emp
l
oyed in [13]
. Howeve
r,
sha
r
pn
ess of
the tran
sition re
gion
a
nd
sup
p
re
ssion
of ha
rmoni
cs
in the
stop
ba
nd n
eed
fu
rth
e
r im
prove
m
ent for t
he
prese
n
ted filters in
[10-13].
In this
pap
er, we
pro
p
o
s
e a
new co
mpact
LPF
with
sha
r
p t
r
ansitio
n an
d
improved
stopb
and. Sh
arp tran
sition
and g
ood
pa
ssba
nd p
e
rfo
r
mance of the
LPF is o
b
tain
ed by u
s
ing t
he
pre
s
ente
d
co
mpleme
ntary recta
ngle
spli
t
ring
DMS
(CRS
R-DMS).
The im
prove
d
sto
pban
d
ma
y
be a
c
hieve
d
as follo
ws. Fi
rst, two
op
en
stub
s a
r
e
pl
ace
d
in th
e
microstri
p
lin
e to ge
nerate
two
transmissio
n
ze
ro
s in tra
n
smi
ssi
on
re
spo
n
se. A third-ord
e
r
LPF usi
ng the
spu
r
line i
s
t
hen
inse
rted i
n
th
e propo
se
d filter for
wid
e
att
enuation
band
width. F
i
nally, two d
u
mbbell
-
shap
ed
DGS
s
with
different len
g
t
hs are em
ployed to
furt
her
wide
n th
e stop
ban
d band
width. T
he
prop
osed
filter featu
r
e
s
co
mpactn
ess b
e
ca
use of
its uniqu
e config
uration
a
nd sl
ow-wave
effe
cts
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 13, No. 1, Janua
ry 2015 : 85 – 9
0
86
of the
emplo
y
ed resonato
r
s. B
a
se
d
on
aforementio
ned
de
sign
p
r
inci
ple
s
, the
prop
osed
LP
F is
impleme
n
ted
and its sim
u
la
tion and mea
s
ureme
n
t results are p
r
e
s
e
n
ted.
2. Design an
d Implementation of the
Nov
e
l Lo
w
p
ass Filter
2.1. Configur
ation and
De
sign of th
e Propose
d
LPF
The co
nfigu
r
a
t
ion of the propo
sed LPF i
s
sh
own in Figure 1, whe
r
e multilayer tech
niqu
e
is use
d
. In the top micro
s
trip pla
ne, two
CRSR-DMSs are et
ched nea
r inp
u
t/output port
s
to
prod
uce initi
a
l two tran
smissi
on
ze
ro
s. Si
nce th
e presented
CRS
R-DM
S exhibits
high
attenuation rate and low
inse
rtion lo
ss in t
he passband, whi
c
h
will be se
en
in the followi
ng
se
ction, sh
arp tran
sition
and go
od p
a
ssba
nd
pe
rforman
c
e of
the prop
osed LPF ca
n
be
achi
eved.
T
w
o
o
pen stubs are pla
c
ed nea
r
th
e CRSR-DM
S
s, re
sulting
in anothe
r two
transmissio
n zeros. A third
-
order
LPF u
s
ing
spu
r
li
ne
is located in
the middle of
the micro
s
tri
p
line an
d its
stopb
and i
s
adopte
d
to
widen
reje
ctio
n ban
dwi
d
th
of the propo
sed filte
r
. In
the
bottom groun
d plan
e, two
dumbb
ell-sha
ped
DGSs
wi
th different le
ngths
are
put
belo
w
the o
p
en
stub
s for b
e
tter ha
rmo
n
ics supp
re
ssion.
By adj
usting
above op
era
t
ed frequ
en
ci
es p
r
op
erly, the
extended
sto
pban
d may b
e
ea
sily obtai
ned
without
affecting the
origin
al sharp tran
sition a
n
d
good p
a
ssb
a
nd perfo
rma
n
c
e for the p
r
o
posed filter.
1
Ca
1
lo
2
lo
2
Ca
wo
lc
wc
p
w
p
l
wp
(a) T
op View
ld
1
a
2
a
wd
db
(b) Bottom Vi
ew
Figure 1. Con
f
iguration of the pro
p
o
s
ed
LPF
2.2. Chara
c
t
e
ristic of
the
CRSR
-
DMS Unit
The layo
ut o
f
the pre
s
e
n
t
ed CRSR-DMS
unit is
depi
cted in
Figure 2,
wh
ere t
w
o
con
c
e
n
tric
split ring
slot
s with
split
s on op
po
site
side
s a
r
e e
t
ched i
n
the
microst
r
ip li
ne.
Con
s
id
erin
g the limited microstri
p
wi
dth in pra
c
ti
cal ap
plicatio
ns, the re
cta
ngle split rin
g
is
adopte
d
inste
ad of the con
v
entional squ
a
re
split ri
n
g
. The wi
dth of the sl
ot Cw
a
nd the di
stan
ce
betwe
en in
n
e
r a
nd
outer re
ctangl
e
sp
lit ring
Cd
are cho
s
en
as the
same
value 0.3
mm
for
desi
gn sim
p
licity. The sub
s
trate u
s
ed in
the simu
latio
n
s and fab
r
ication is Arlon
Cucla
d
250
(tm)
with a
relativ
e
diele
c
tri
c
consta
nt of 2.5
5
and
a thi
c
kness of
1.5 m
m
. The
width
of the mi
cro
s
t
r
ip
line W is cho
s
en to be 4.5
mm corresp
ondin
g
to a chara
c
te
risti
c
impeda
nce of 50
Ω
. The length
of the splits Cg is set a
s
0.6 mm.
Figure 3
sho
w
s
simul
a
ted
transmissio
n
respon
se
s of
the CSSR-DMS unit with
different
length
s
Ca a
nd width
s
Cb.
It can be cle
a
rly see
n
that the CSSR-DMS uni
t has sharp atten
uati
on
rate
and
little insertio
n lo
ss in
the
pa
ssband.
Moreo
v
er, it can
provide two o
b
v
ious
attenua
tion
pole
s
. The
sup
e
rio
r
cha
r
acte
ri
stic of
the pr
e
s
en
ted CSSR-DMS is very helpful for the
impleme
n
tation of
high
-p
erform
an
ce
L
P
F. We
co
ul
d al
so fin
d
th
at for
a fixed
Ca
or Cb, b
o
th
resona
nt freq
uen
cie
s
at the attenuation
pole
s
de
crea
se when
Cb
or Ca increa
ses. Fu
rtherm
o
re,
the insertion l
o
ss of the p
a
s
sban
d bet
ween the t
w
o a
ttenuation p
o
l
e
s
slightly in
crea
se
s when
Cb
increa
se
s, wh
ich is g
ood fo
r har
m
oni
cs
suppressio
n
of LPF.
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TELKOM
NIKA
ISSN:
2302-4
046
A Novel
Com
pact Mi
cro
s
tri
p
Lowpa
ss Fil
t
er with Sharp Tran
sition a
nd… (Pin
gjua
n Zhang
)
87
W
Cb
Ca
Cg
Cd
Cw
Figure 2. Layout of the CRSR-DMS unit
12345
6
789
1
0
-30
-25
-20
-15
-10
-5
0
Ca=7.0m
m
Ca=8.0m
m
Ca=9.0m
m
|S
21
| (d
B)
F
req
uen
c
y
(GHz
)
(a)
123
45
6789
1
0
-3
0
-2
5
-2
0
-1
5
-1
0
-5
0
Cb
=3.
2
m
m
Cb
=3.
6
m
m
Cb
=4.
0
m
m
|S
21
| (
d
B
)
F
r
e
q
ue
n
c
y
(
GHz)
(b)
Figure 2. Effects of the le
ngth
Ca
(Cb
=
3.6
mm) (a
) and
the width
Cb
(Ca
=
8.0 mm
) (b
) on the
transmissio
n respon
se of the CRSR-DM
S
2.3. Third-Or
d
er LPF Usi
ng Spurline
The sp
urlin
e with its inhe
rently compa
c
t layout
is realized by etchi
ng a folded sl
ot in the
microstri
p
lin
e. Similar wit
h
the defe
c
ted struct
u
r
e
s
, the spurli
n
e
can
also
p
r
ovide ex
cell
en
t
stopb
and [14
-
15]. It is noticed that the f
r
equ
en
cy
re
spon
se of the
spu
r
line m
a
y be re
pre
s
e
n
ted
by a parallel
LC ci
rcuit with the circuit p
a
ra
m
e
ters co
mputed from
followin
g
expression
s:
22
2
2
00
0
1
,
24
c
c
f
CL
Z
ff
f
C
(1)
Whe
r
e
c
f
is th
e 3-dB
cut-of
f freque
ncy,
0
f
is the
freq
ue
ncy of th
e att
enuatio
n pol
e
and
0
Z
is
the cha
r
a
c
teri
stic impe
dan
ce of the micro
s
trip line.
The
equivale
nt indu
ctan
ce L
and
ca
pacita
n
ce
C of the
spurline d
epe
nd
s on
the
dimen
s
ion
s
o
f
the defecte
d slot. As
sh
own i
n
Figu
re
4(a
)
, wh
en the wi
dth pw
and
slot widt
h wp
are fixed to be 3.8 mm and 0.4 mm respectively, the
equivalent L is pro
portio
n
a
l
to the length pl
while the eq
ui
valent C kee
p
s
nea
rly unch
ange
d. In
Figure 4(b), whe
n
the length p
l
and the width
pw i
s
set
to
be 5.0
mm
a
nd 3.0
mm
correspon
dingl
y, the eq
uivalent L
slig
htly
increa
se
s
wh
ile
the eq
uivale
nt C
de
cre
a
ses
rapi
dly a
s
the
slot
wid
t
h wp
in
cre
a
s
e
s
. The
r
efo
r
e, the requi
red
circuit p
a
ra
m
e
ters may b
e
easily
obtain
ed by tuni
n
g
the dime
nsio
ns of th
e spu
r
line. Ba
sed
on
the filter de
si
gn theo
ry [1], a third
-
o
r
de
r LPF
is d
e
si
g
ned a
nd its
configuration
can be fo
und i
n
Figure 1(a
)
. Two spurli
ne
s with the sa
me size are
use
d
to con
s
truct the lum
ped indu
ctan
ce
element
s and
the cro
s
s-ju
n
c
tion op
ene
d stub is
a
dopt
ed to reali
z
e the sh
unt ca
p
a
citan
c
e.
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Vol. 13, No. 1, Janua
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0
88
4.
2
4
.
5
4.
8
5
.
1
5.
4
5
.
7
6.
0
1.2
1.4
1.6
1.8
2.0
2.2
L
C
p
l
(
mm)
L (n
H)
0.
10
0.
15
0.
20
0.
25
0.
30
0.
35
0.
40
C (
p
F
)
(a)
0.
1
0
.
2
0.
3
0
.
4
0.
5
0.
4
0.
6
0.
8
1.
0
1.
2
1.
4
w
p
(
mm)
C (pF)
L (nH)
0.
30
0.
35
0.
40
0.
45
0.
50
0.
55
0.
60
L
C
(b)
Figure 4. Equivalent L-C va
lue versus th
e l
ength pl (a
) and the widt
h wp of the spurlin
e
0
2
468
1
0
-50
-40
-30
-20
-10
0
Ful
l
-w
ave
Cir
c
u
i
t
Magnitude
(
d
B)
Fr
e
q
ue
ncy
(
G
H
z
)
21
S
11
S
Figure 5. Full-wave a
nd ci
rcuit simul
a
ted
S-par
a
m
eters of the third-orde
r LPF u
s
i
ng sp
urlin
e
The dime
nsi
ons of thi
s
third
-
orde
r LPF
are: pl
=3.
6
mm, pw=4.1 mm, wp=0.4 mm,
wc=1
0.2 mm,
lc=5.35
mm.
Figure. 5
plot
s the
ci
rc
uit a
nd full-wave
simulate
d
re
sults a
nd
a go
od
agre
e
me
nt betwee
n
the two
can b
e
se
en. The di
sc
repan
cy at the
stopb
and i
s
resulte
d
from t
he
distrib
u
ted effects a
nd the
radiatio
n loss which ar
e
no
t consi
dered i
n
ideal ci
rcuit simulation. A
s
sho
w
n in Fig
u
re. 5, the 20-dB rej
e
ctio
n band is
fro
m
6.2 GHz t
o
8.1 GHz wi
th an attenua
tion
pole at
7.36
GHz.
A
lo
cal
pea
k
o
c
curs arou
nd 9.
0
G
H
z in th
e full
-wave
simul
a
tion b
u
t it ha
s
n
o
effective ban
dwidth
and m
a
y be supp
re
ssed by
a du
mbbell
-
shape
d
DGS. Due to
the
co
mpa
c
t
layout an
d g
ood
reje
ction
ch
aracte
risti
c
of
the th
i
r
d
-
orde
r
LPF, it
is e
m
be
dded
in o
u
r p
r
op
o
s
ed
filter for impro
v
ed stopb
and
.
3. Experimental Validati
on
The propo
se
d LPF sh
own in Figure 1 is
desi
gne
d ba
sed on p
r
eviou
s
investig
atio
ns. The
final optimi
z
e
d
phy
sical di
mensi
o
n
s
of
the filt
er a
r
e:
Ca
1=8.0 m
m
, Ca2
=
6.3
mm, Cg
=0.6
mm,
Cw=Cd=0.3 mm,
Cb=3.6 mm,
wo=4
.2 mm,
lo1=8.8 mm,
lo2=5.8
mm, wd=0.3
mm, ld=5.0
mm,
a1=2.3 mm, a2=1.9 mm, db=14.65 m
m
, while the
spu
r
line
s
an
d
the open stu
b
s have the
same
spe
c
ification
as in Figu
re 5
.
To better illustrate the working
principl
e of the proposed f
ilter, the compari
s
on of th
e
simulate
d tra
n
smi
ssi
on respon
se results of CRS
R-o
p
en stu
b
, CRS
R-o
pen
stub
-spu
rline
and t
he
prop
osed
LPF are
cond
ucted and
sho
w
n in
Figu
re
6. It is foun
d that when
there i
s
o
n
ly
two
CRS
R-
DMS
s
and
two
op
e
n
stu
b
s,
six
tr
ansmi
s
s
ion
zero
s
(4.32/5.
33/5.
47/7.35/
8.32/10.19
G
H
z)
are p
r
od
uce
d
and a sha
r
p tran
sition
is achieved.
As the third-orde
r LPF u
s
ing
spu
r
line
is
embed
ded, t
he 20
-dB
reje
ction b
and
re
ach
e
s
up to
10.39 G
H
z e
x
cept a
small
pea
k a
r
ou
nd
9.0
GHz. By inserting ad
ditio
nal two du
m
bbe
ll-sh
ape
d
DGSs, a d
eepe
r and
wider
stopba
n
d
is
obtaine
d an
d
the sim
u
late
d 20-dB sto
p
band i
s
from
4.25 G
H
z to
more th
an 1
5
.
0 GHz. It is
also
Evaluation Warning : The document was created with Spire.PDF for Python.
TELKOM
NIKA
ISSN:
2302-4
046
A Novel
Com
pact Mi
cro
s
tri
p
Lowpa
ss Fil
t
er with Sharp Tran
sition a
nd… (Pin
gjua
n Zhang
)
89
found from Fi
gure 6 that th
e improve
d
st
opba
nd is
rea
lized without affecting
the sha
r
p
tra
n
siti
on
and lo
w insertion loss of the passb
and.
03
6
9
1
2
1
5
-60
-50
-40
-30
-20
-10
0
|S
21
| (dB
)
Fre
q
u
e
ncy
(G
H
z
)
C
R
S
R
-
O
pe
n S
t
ub
C
R
S
R
-
O
pe
n S
t
ub
-S
p
u
r
line
P
r
op
ose
d
LP
F
Figure 6. Simulated tran
sm
issi
on re
sp
on
se
re
sult
s of CRS
R-ope
n stub, CRSR-open
stub-
spu
r
line a
nd the pro
p
o
s
ed f
ilter
Figure 7. Photograp
h of
the fabricated L
P
F
03
69
1
2
1
5
-60
-50
-40
-30
-20
-10
0
M
e
asu
r
em
ent
Si
m
u
lat
i
on
Magnitude (
d
B
)
F
r
e
q
ue
nc
y
(
G
Hz
)
21
S
11
S
Figure 8. Simulated an
d measure
d
S-
pa
ramete
rs of t
he fabri
c
ated
LPF
The ph
otogra
ph of the fab
r
icate
d
LPF i
s
sh
own in F
i
gure
7. The
simulate
d fre
quen
cy
respon
se
re
sult agre
e
s
well with the
measured
re
sult a
s
de
picted in Figu
re
8 and
a sli
ght
differen
c
e
be
tween th
e
si
mulation
and
mea
s
ureme
n
t is d
ue to
the fabri
c
atio
n toleran
c
e.
As
expecte
d, the
mea
s
u
r
ed
re
sult
sho
w
s th
at t
he p
r
op
osed LPF
provides a
sh
arp
tran
sition
ban
d
from 3.8
8
G
H
z to 4.1
4
GHz
with 3
dB and
44.3
5
dB
reje
ctio
n re
sp
ectivel
y
, resulting i
n
an
attenuation
rate of 159
d
B
/GHz. T
he
suppressio
n
le
vel above 2
0
dB is from 4
.
07 GHz to m
o
re
than 15
GHz in spite
of a
small p
e
a
k
at 12.3 G
H
z.
In the pa
ssb
and fro
m
d
c
to 2.06 G
H
z, the
Evaluation Warning : The document was created with Spire.PDF for Python.
ISSN: 23
02-4
046
TELKOM
NI
KA
Vol. 13, No. 1, Janua
ry 2015 : 85 – 9
0
90
inse
rtion l
o
ss is l
e
ss tha
n
0.3 dB. Th
e return l
o
ss i
s
belo
w
-12.5
dB in the
wh
ole p
a
ssba
nd
. In
addition, the
actual o
c
cupi
ed physi
cal a
r
ea of
the pro
posed filter is only 35.25* 1
6
.15 mm
2
.
4. Conclusio
n
A novel micro
s
trip LPF
with
sha
r
p tra
n
siti
on and i
m
pro
v
ed stop
band
is propo
se
d and its
desi
gn p
r
o
c
e
dure i
s
de
scribed. By usin
g t
he pre
s
e
n
t
ed CRS
R-DMS resonato
r
, the pro
p
o
s
ed
LPF en
able
s
sh
arp
atten
uation
rate
and l
o
w in
sertion l
o
ss
o
f
the pa
ssba
nd. Mea
n
whi
l
e,
harm
oni
c re
spon
se of the prop
osed filter is e
ffectivel
y suppresse
d
by
open stu
b
s, a third-order
LPF using
sp
urline a
nd the dumbb
ell-shape
d DGS.
The mea
s
u
r
e
d
result of th
e fabricated
LPF
sho
w
s that
at
tenuation
rate rea
c
he
s
15
9 dB/G
Hz
an
d a
wi
de
stop
band
is a
c
hie
v
ed. With
go
od
passb
and
an
d stop
ban
d
perfo
rman
ce,
simpl
e
de
si
gn p
r
o
c
edu
re and
a
co
mpact
si
ze,
the
prop
osed LP
F make
s itsel
f
useful for ap
plic
atio
ns in
mode
rn com
m
unication sy
stem
s.
Referen
ces
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Hong J, Lancaster M.
Microstrip Filters for
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a
ve Appl
icatio
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e
w
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i
l
e
y, 2
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121.
[2]
Yang M,
Xu J,
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hao Q, Pen
g
L, Li G. Co
mpac
t Broa
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opba
nd
Lo
w
p
ass F
ilters Usi
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H. Design of
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i
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h
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w
i
d
e
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i
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,
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,
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a J. Novel Co
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apered 1-
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eng H, W
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g
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hang C,
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hu L. Com
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o
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ilter
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li
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a
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w
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ilter
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i
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chnol. Lett.
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ang
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i
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l
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tted-
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o
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ilter.
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aher H. Ultra
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ilt
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g
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iangul
ar R
e
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our
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oh T
.
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p
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ilter
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.
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o
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ilter
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